Attaching GPSBabel operations to a single mouse click

Robert Nixon offers this tip for OS/X users to associate
GPSBabel commands with a single click.

The following is an applescript that will allow you to click
once and convert a file using gpsbabel without using the command
line. What is better is that you can add more functionality and
convert more than one file by just redefining the variables after
the "do shell script" command and adding another "do shell script"
command.